Story highlights

Mosul is a hell of "endless, throat-grabbing, suffocating sorrow"

From the front lines: "civilians cowering under staircases ... children screaming, parents helpless to protect them"

Mosul, Iraq (CNN)A Humvee screams into the field clinic a few kilometers from western Mosul's current front line. A teenage girl is carried out, listless. An elderly man is in complete shock, unable to utter a word, and is helped towards a bed. A woman struggling to breathe is quickly given oxygen.

Ten-year-old year old Mariam Salim and her older sister, Ina'am, are being tended to in the back.

"My parents are under the rubble, (another) sister is dead. I saw her," Ina'am mutters, her lips quivering.

Just as the family was trying to flee, the two girls say, a mortar hit their house causing it to collapse. The rest of the family is buried under the rubble.

Mariam leans over to wipe the Betadine antiseptic off her sister's face -- the reality of what she has said perhaps not quite sinking in, or maybe she just needs something to focus on, a distraction from a loss she cannot yet comprehend.

Her sorrow seems to come in waves. Her body shakes as her eyes fill with tears, but just as quickly she is angrily asking questions, yelling to an older brother who made it out, "We were trying to get to you!" and then turning around and calmly cleaning Ina'am's face.

Their neighborhood is still under ISIS control, although the Iraqi forces are within eyesight and earshot. Those forces were not able to reach the siblings' home or their family members trapped under the destroyed house. They cling to a hope that at least maybe their parents and younger brother may still somehow be alive.

We drive closer to the frontline. Plumes of smoke rise, the explosions rumbling in the distance. The targets are ISIS fighters, but with each blast comes the reality that in the homes and streets hit -- whether by airstrikes, artillery, or ISIS bombs -- are civilians cowering under staircases, in basements. Children screaming, parents helpless to protect them.

Earlier, an Iraqi commander, visibly upset, had told us of corpses they pulled from under the rubble in one neighborhood. A mother was still cradling her baby.

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'Where have you been for the last three years?'

Stumbling through the debris-strewn streets, past the blown-out buildings and burned-out vehicle husks, those who survived make their way towards the Iraqi forces. Escape rarely comes before the fighting picks up as Iraqi troops move in on ISIS forces. ISIS executes anyone who tries to flee when ISIS fighters are not otherwise occupied.

They arrive breathless, voices shaking, single sentences that hardly encompass what they have been through.

"Where have you been for the last three years?" a woman shouts at Iraqi troops.

Photos:Life, death and sorrow for Mosul civilians as war rages on

Photos:Life, death and sorrow for Mosul civilians as war rages on

Ten-year-old Mariam Salim cries as she is treated at a makeshift clinic in western Mosul. She was trying to make a run for it with her family on June 4, 2017, when their house collapsed from an explosion. Most in her family are buried under the rubble of what was their home.

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Photos:Life, death and sorrow for Mosul civilians as war rages on

Salim siblings: From left to right, Mariam, Ina'am and Shamil Salim, got out of their house as it collapsed, killing a sister and burying a brother and both parents under the rubble. Iraqi security forces cannot get to the house because it is still under ISIS control.

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Photos:Life, death and sorrow for Mosul civilians as war rages on

An Iraqi man shouts that ISIS killed his son when he tried to escape from the Zinjili neighborhood in western Mosul to a government-controlled area. ISIS took control of Mosul -- the largest city in Iraq -- in June 2014. The operation to liberate it started in October 2016 -- and is still ongoing.

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Photos:Life, death and sorrow for Mosul civilians as war rages on

Salim Sa'ed smiles and hugs his neighbor after they both were able to escape the Zinjili neighborhood, one of the very few districts still under ISIS control in western Mosul, on June, 4, 2017.

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Photos:Life, death and sorrow for Mosul civilians as war rages on

After years living under ISIS, Iraqi civilians escape the fierce battle raging in the Zinjili neighborhood in western Mosul -- one of the very few districts still under ISIS control -- on June, 4, 2017. People passing by a CNN crew said since the operation to liberate Mosul from ISIS started in October 2016, food has been getting scarcer by the day. Some said they have been living on soup made only of water and flour.

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Photos:Life, death and sorrow for Mosul civilians as war rages on

Iraqi civilians escape the fierce battle raging in the Zinjili neighborhood in western Mosul on June 4, 2017. As these women passed by Iraqi security forces, the woman in the orange hijab screamed, "Where were you for the last three years?"

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Photos:Life, death and sorrow for Mosul civilians as war rages on

Dave Eubank from the "Free Burma Rangers" volunteer organization carries a little girl to safety after spotting her hiding under her dead mother's hijab for two days. The child was rescued in western Mosul as gunfire raked the area. Photo courtesy of Free Burma Rangers (www.freeburmarangers.org/)

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"Twenty days ago we tried to escape, they (ISIS fighters) caught him, shot him four times in the head," a man sobs. "My brother."

There is deep sorrow. There is anger. There is relief.

As ISIS is being squeezed into even smaller territory -- a handful of neighborhoods and Mosul's old city -- the civilians held hostage are running out of food.

Umm Abed has a family of 11

"We were eating flour and water." She says. It was only enough to feed the children, to ease their hunger pains. She and her husband stayed without food for four days.

Also on the front line is a forward field clinic manned by ex-US Army Special Forces soldier Dave Eubank and his team with the Free Burma Rangers, a non-governmental service organization.

Just days earlier they responded to a call from one of the Iraqi units.

"They said civilians coming, a lot (of them) shot. We got there and a guy came crying, crying, he said, 'My daughter was shot in front of me, her head was blown off.'" Eubank recalled.

The field was littered with dozens of bodies massacred by ISIS fighters as they were trying to flee. Men, women, young, old. Children shot in the face.

Thirteen bodies ... and then, movement

"We saw these 13 bodies and then we saw movement. Here they are, look against the wall, these are all dead people." He shows us a photo on this phone. Bodies crumpled against each other.

After the photo was taken, life appears and the effort to save life is fast.

One man is alive, he moves his arm. From underneath a black hijab a little girl peers out. Her mother had been dead for two days. The little girl hid against her mother's corpse.

American forces supporting Iraqis with air assets drop a curtain of smoke. Using an Iraqi tank for cover Eubank and others move as close as they can.

"We got there and then the smoke lifted," Eubank said later. "And then ISIS just hammers them. And the people there are like, 'Come! come!' And the little girl gets out from under her dead mother's hijab and she sees us -- the tank is shooting, you know. "

"I called the Americans, I said, 'Please give me smoke again right now.' The Iraqis are already in on this. So the Americans dropped this perfect curtain of smoke I ran grabbed her.

"She was screaming, unwilling to let her mother go. No one knows her name, she still hasn't said a word."

The next morning, Eubank said, another man somehow managed to escape and told them of others who were still alive.

"With a brave Iraqi soldier, we ran across the road -- ISIS is on three sides of us, we can hear them talking. Crawled through, found a girl up the street, threw a rope to her. She tied herself. (She was) three days no sleep no water, wounded."

They managed to safely drag her over the rubble and rocks.

The depth of the suffering here impossible to articulate.

"It is hell," an elderly woman in a wheelchair said softly.

A hell that we cannot even begin to imagine.

The incomprehensible brutality of life under ISIS, the public executions, beheadings, school curriculums that taught of slaughter, mandatory black niqabs and long beards; smoking, cell phone, satellite TV bans. To endure that for three years followed by the incessant bombardment, fear and starvation.

People here have lost just about everything.

There is no past blueprint for this war, no one has fought an enemy like ISIS holding civilians hostage in this type of a dense urban battlefield. There are no words to comfort those who survive.